Here is a possible way to express the meaning accurately:
"I have the item you requested, which is 33 centimeters long. However, I don't have it in a 30-centimeter length at the moment due to the high cost of raw materials. Nevertheless, I value our long-term partnership and I am willing to sell you the 30-centimeter one at the same price as before. Thank you for your understanding."
I give you do is 33 cm, 30 cm long without spot, is to buy the price of raw materials is very expensive, but also according to the original price I give you do 30 cm long! For the sake of our long-term cooperation